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IS 1785:2000 (Part 2) is the Indian Standard (BIS) for plain hard-drawn steel wire for prestressed concrete, part 2: as the drawn wire. This standard covers the requirements for plain hard-drawn steel wire used for prestressed concrete in its 'as drawn' condition (without stress-relieving treatment). It specifies the chemical composition, physical tolerances, and mechanical tests such as tensile and reverse bend tests to ensure wire suitability for prestressing applications.
plain hard-drawn steel wire for prestressed concrete, Part 2: As the drawn wire
! Wire in the 'as drawn' condition has higher relaxation losses compared to stress-relieved wire (covered in Part 1). Use only where structural design explicitly accounts for higher relaxation.
! A light film of rust is generally permissible and can improve bond, but the wire must be free from deep pitting, scales, or surface defects.
ISO 6934-2:2021International Organization for Standardization (ISO), International
HighCurrent
Steel for the prestressing of concrete — Part 2: Cold-drawn wire
Covers cold-drawn round steel wire (plain, indented, or patterned) for prestressing concrete.
ASTM A421/A421M-21American Society for Testing and Materials (ASTM), USA
HighCurrent
Standard Specification for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete
Specifies requirements for uncoated, stress-relieved, high-carbon steel wire for prestressed concrete.
BS 5896:2012British Standards Institution (BSI), UK
MediumCurrent
Steel for the prestressing of concrete. Specification for high tensile steel wire and strand for the prestressing of concrete
Broader scope covering both wire and strand, but its requirements for wire are similar.
EN 10138-2:2009European Committee for Standardization (CEN), Europe
HighWithdrawn
Prestressing steels - Part 2: Wire
Previous European standard for prestressing wire, now harmonized under the ISO framework.
Key Differences
≠IS 1785 specifies two types: plain and indented wire. Modern international standards like ISO 6934-2 also include patterned (e.g., chevron) wires.
≠IS 1785 defines a single class for relaxation. In contrast, ISO 6934-2 defines three classes: Class 1, Class 2 (normal relaxation), and Class 3 (low relaxation), which is the modern default for most applications.
≠Chemical composition in IS 1785 is prescriptive with defined ranges (e.g., Carbon 0.75-0.85%). ASTM A421 and ISO 6934-2 often allow for more flexibility, providing 'heat analysis' ranges and allowing composition to be optimized by the manufacturer to meet performance criteria.
≠IS 1785 specifies proof stress at 0.1% non-proportional elongation. Many international standards, including ASTM A421, may also use or refer to yield strength determined at 1% total extension under load, and ISO 6934-2 also uses 0.1% proof stress (f_p0,1).
Key Similarities
≈All standards are based on the same manufacturing process: cold-drawing high-carbon steel rod followed by a continuous stress-relieving heat treatment.
≈The fundamental purpose and application are identical: to provide a high-strength tensioning element for inducing and maintaining compressive forces in prestressed concrete structures.
≈Core mechanical tests are similar, including tensile strength, proof/yield strength, elongation, and some form of ductility test (e.g., bend test).
≈All standards require the material to be free from defects like seams, splits, or surface imperfections that could be detrimental to its performance in service.
Parameter Comparison
Parameter
IS Value
International
Source
Tensile Strength (UTS) - 7 mm wire
1725 N/mm² (for Grade 1725)
1770 MPa (for Grade Y1770C)
ISO 6934-2:2021
0.1% Proof Stress (min)
85% of specified UTS
1560 MPa (approx. 88% of UTS for Grade Y1770C)
ISO 6934-2:2021
Elongation at fracture (min)
4% (on 200 mm gauge length)
4% (on 10 in. / 254 mm gauge length)
ASTM A421/A421M-21
Relaxation at 1000h (70% initial load)
Max 2.5%
Max 2.5% (for Low Relaxation / Class 3 wire)
ISO 6934-2:2021
Phosphorus (P) content, max
0.040%
0.040%
ASTM A421/A421M-21
Sulphur (S) content, max
0.040%
0.050%
ASTM A421/A421M-21
Reverse Bend Test (5mm wire)
Minimum of 3 bends without failure
Minimum of 2 bends without failure
ISO 6934-2:2021
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Carbon content0.60 to 0.90 percent
Sulphur content (max)0.050 percent
Phosphorus content (max)0.050 percent
Standard nominal diameters3.0, 4.0, and 5.0 mm
Tolerance on nominal diameter± 0.05 mm
Tables & Referenced Sections
Key Tables
Table 1 - Chemical Composition
Table 2 - Nominal Sizes and Tolerances
Table 3 - Tensile Strength and Bend Test Requirements
What is the difference between IS 1785 Part 1 and Part 2?+
Part 1 covers cold-drawn stress-relieved wire, while Part 2 covers wire in the 'as drawn' condition which has not undergone a stress-relieving thermal treatment.
What are the common sizes of 'as drawn' prestressing wire?+
The standard nominal diameters are typically 3.0 mm, 4.0 mm, and 5.0 mm.
What is the maximum allowable sulphur and phosphorus content?+
Both Sulphur and Phosphorus are limited to a maximum of 0.050 percent each.